Notes, summaries, assignments, exams, and problems for Biology

The Human Heart: Structure and Function

The heart is a muscular organ situated between the lungs, slightly to the left. Its walls, known as the myocardium, are responsible for pumping blood.

It is made up of four chambers:

• Two atria (upper chambers)
• Two ventricles (lower chambers)

The heart also contains valves that regulate blood flow:

• The tricuspid valve connects the right atrium and the right ventricle.
• The mitral valve connects the left atrium and the left ventricle.

Understanding the Cardiac Cycle

The cardiac cycle is the sequence of events that occurs with each heartbeat. As the heart beats, it circulates blood through the body's pulmonary and systemic circuits.

There are two main phases of the cardiac cycle:

• Diastole Phase: The heart ventricles

The structural organization of eukaryotic cells is remarkably complex and compartmentalized, reflecting the diverse functions these cells perform. Eukaryotes encompass a wide array of organisms, including plants, animals, fungi, and protists. Below is a detailed exploration of the structural components of eukaryotic cells:

1. Cell Membrane (Plasma Membrane)

• Composition: The cell's outer boundary is formed by a phospholipid bilayer with embedded proteins and other molecules.
• Function: It regulates the passage of substances into and out of the cell, acting as a selective barrier.

2. Cell Wall (in some cells)

• Present in: Plant cells, fungal cells, and some protists.
• Composition: A rigid structure made of cellulose in plants and chitin in fungi.
• Function:

Histogenesis of Blood Tissue

Histogenesis refers to the origin and development of cells.

Development of Granulocytes (Myelopoiesis)

Granulocytes are cells with granular cytoplasm, including neutrophils, eosinophils, basophils (cells ending in -phil), and mast cells.

Stages of Granulocyte Development:

• Myeloblast
• Promyelocyte
• Myelocyte (stage when granules appear)
• Metamyelocyte

Origin of Blood Cells

All blood cells originate from the Hematopoietic Stem Cell. These cells differentiate after being stimulated by hormones or interleukins. For example, B-lymphocytes become plasma cells after being stimulated by IL-2 in order to fight infections.

Characteristics and Composition of Blood

General Characteristics of Blood

• Consists of blood plasma and matured blood

Understanding Kidney Function

As capillaries exit organs, they converge into larger blood vessels, veins, which eventually return the blood to the heart at the right atrium.

Abnormal Kidney Function:

An individual's kidneys are unable to remove waste, the medical treatment known as hemodialysis. Use a dialysis machine 'artificial kidney' is only temporary, until the patient recovers normal kidney function or receives a kidney transplant. Blood is put in close contact with a special solution similar to blood plasma. The semipermeable membrane allows urea and other waste materials to exit the blood and prevents the escape of blood cells.

Painful Stones:

The substances transported in the urine can trigger the formation of crystals, commonly referred... Continue reading "Understanding Kidney Function, Stones, and Blood Disorders" »

Brain Anatomy and Functions

The human brain is a complex organ, the control center of the nervous system. Below are key parts and their vital roles:

Cerebral Cortex

The outermost layer of neural tissue that covers the brain, responsible for higher-level functions like thought, language, and memory.

Corpus Callosum

A large bundle of nerve fibers connecting the two cerebral hemispheres, facilitating communication and influencing logic and creativity.

Hypothalamus

A crucial part of the brain that links the nervous system to the endocrine system via the pituitary gland, regulating essential bodily functions.

Thalamus

A major relay station for sensory information, also regulating sleep, alertness, and consciousness.

Midbrain

Involved in motor movement, particularly

The Central Dogma of Molecular Biology

Replication - General Characteristics:

• DNA replication is semiconservative: each strand in the DNA double helix acts as a template for the synthesis of a new, complementary strand. The new two daughter molecules of DNA have a new strand and an old one.
• DNA polymerase III: is the enzyme that adds nucleotides to the growing DNA chain, incorporating only those that are complementary to the template. DNA polymerase III has the following characteristics:
  • It can only read a template in 3’-----5’ direction so the new strand grows in 5’----3’ direction.
  • It needs a pre-existing strand of nucleotides called a primer which provides a 3’-OH end to bind new nucleotides.
  • It is able to repair the mistakes by removing

Natural Selection: Principles of Adaptation

Natural selection is the principle that variations in the biology or behavior of a species result in some individuals possessing traits that confer an advantage in survival. This process is highly dependent on the environment.

Individuals with these advantageous traits are more likely to survive, prosper, and reproduce. Over time, the population becomes dominated by individuals exhibiting these beneficial biological or behavioral characteristics. Offspring of the same species can be born with mutations, introducing new variations. Natural selection drives populations to become adapted, or increasingly well-suited, to their environments over time. This process relies on the environment and requires existing... Continue reading "Understanding Natural Selection and Brain Functions" »

The Human Sensory System: Receptors and Organs

Understanding Sensory Receptors

Sensory receptors are specialized structures responsible for detecting changes (stimuli) in the world around us and converting them into nerve impulses. These impulses then travel to a higher nerve center where perception begins. Sensory receptors can be simple groups of nerves or, more often, special cells that join together to form the sensory organs.

Classification of Sensory Receptors

Receptors are typically classified based on the type of stimulus they detect:

• Photoreceptors: Detect light stimuli and are found in the eyes.
• Mechanoreceptors: Stimulated by changes in movement, such as pressure, contact, or sound waves. These include receptors in the skin, muscles, and

Arthritis: Inflammation of the Joints

Arthritis is a condition where the joints become inflamed, swollen, and warm to the touch. It can also cause decreased mobility and joint deformities.

Osteoarthritis: A Common Type of Arthritis

Osteoarthritis is a chronic, non-inflammatory condition characterized by progressive degeneration of the cartilage and joints.

Gout: Painful Inflammation of Joints

Gout is a type of arthritis that involves painful inflammation of the joints. It usually begins abruptly and is accompanied by redness and swelling.

Rheumatism: Similar to Osteoarthritis

Rheumatism is similar to osteoarthritis but typically occurs in individuals between the ages of 25 and 55.

Osteoporosis: Decrease in Bone Mass

Osteoporosis is a condition characterized... Continue reading "Common Types of Arthritis and Other Joint Conditions" »

Enzymes: Proteins that Function as Biological Catalysts